android bitmap compress
android的照相功能随着手机硬件的发展，变得越来越强大，能够找出很高分辨率的图片。
有些场景中，需要照相并且上传到服务，但是由于图片的大小太大，那么就上传就会很慢(在有些网络情况下)，而且很耗流量，要想速度快，那么就需要减小图片的大小。减少图片的大小有两种方法，1. 照小图片； 2. 压缩大图片。 照相时获取小图片一般不太符合要求，因为，图片的清晰度会很差，但是这种情况有个好处就是应用速度会快些； 压缩图片，就是把大图片压缩小，降低图片的质量，在一定范围内，降低图片的大小，并且满足需求（图片仍就清晰）。下面组要是介绍图片的压缩：
1. 照相请查看http://blog.csdn.net/luhuajcdd/article/details/8826587->想要保存图片到制定目录，启动Camera应用时，需要指定文件
2. 压缩过程：
2.1 从图片路径中读取图片(图片很大，不能全部加在到内存中处理，要是全部加载到内存中会内存溢出)
[java]view plaincopy
finalBitmapFactory.Options options =newBitmapFactory.Options();
options.inJustDecodeBounds =true;
BitmapFactory.decodeFile(filePath, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options,480,800);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds =false;
Bitmap bm = BitmapFactory.decodeFile(filePath, options);
2.2 处理图片旋转
[java]view plaincopy
intdegree = readPictureDegree(filePath);
bm = rotateBitmap(bm,degree) ;
[java]view plaincopy
privatestaticintreadPictureDegree(String path) {
intdegree =0;
try{
ExifInterface exifInterface =newExifInterface(path);
intorientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
switch(orientation) {
caseExifInterface.ORIENTATION_ROTATE_90:
degree =90;
break;
caseExifInterface.ORIENTATION_ROTATE_180:
degree =180;
break;
caseExifInterface.ORIENTATION_ROTATE_270:
degree =270;
break;
}
}catch(IOException e) {
e.printStackTrace();
}
returndegree;
}
[java]view plaincopy
privatestaticBitmap rotateBitmap(Bitmap bitmap,introtate){
if(bitmap ==null)
returnnull;
intw = bitmap.getWidth();
inth = bitmap.getHeight();
// Setting post rotate to 90
Matrix mtx =newMatrix();
mtx.postRotate(rotate);
returnBitmap.createBitmap(bitmap,0,0, w, h, mtx,true);
}
2.3压缩图片
[java]view plaincopy
bm.compress(Bitmap.CompressFormat.JPEG,30, baos);//30 是压缩率，表示压缩70%; 如果不压缩是100，表示压缩率为0
完整的方法代码：
[java]view plaincopy
publicstaticBitmap getSmallBitmap(String filePath) {
finalBitmapFactory.Options options =newBitmapFactory.Options();
options.inJustDecodeBounds =true;
BitmapFactory.decodeFile(filePath, options);
// Calculate inSampleSize
options.inSampleSize = calculateInSampleSize(options,480,800);
// Decode bitmap with inSampleSize set
options.inJustDecodeBounds =false;
Bitmap bm = BitmapFactory.decodeFile(filePath, options);
if(bm ==null){
returnnull;
}
intdegree = readPictureDegree(filePath);
bm = rotateBitmap(bm,degree) ;
ByteArrayOutputStream baos =null;
try{
baos =newByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.JPEG,30, baos);
}finally{
try{
if(baos !=null)
baos.close() ;
}catch(IOException e) {
e.printStackTrace();
}
}
returnbm ;
}
[java]view plaincopy
privatestaticintcalculateInSampleSize(BitmapFactory.Options options,
intreqWidth,intreqHeight) {
// Raw height and width of image
finalintheight = options.outHeight;
finalintwidth = options.outWidth;
intinSampleSize =1;
if(height > reqHeight || width > reqWidth) {
// Calculate ratios of height and width to requested height and
// width
finalintheightRatio = Math.round((float) height
/ (float) reqHeight);
finalintwidthRatio = Math.round((float) width / (float) reqWidth);
// Choose the smallest ratio as inSampleSize value, this will
// guarantee
// a final image with both dimensions larger than or equal to the
// requested height and width.
inSampleSize = heightRatio < widthRatio ? widthRatio : heightRatio;
}
returninSampleSize;
}